The present invention relates generally to optical or magneto-optical disk storages, and more particularly to an optical or magneto-optical disk storage which automatically adjusts recorded/reproduced levels of a number of kinds of optical or magneto-optical disks having different recorded/reproduced levels to optimum recorded/reproduced levels.
In an optical disk storage adopting a constant angular velocity (CAV) method, recording densities between inner and outer tracks are different, and thus a signal reproduced at the inner track has a reproduced level lower than that of a signal reproduced at the outer track. Accordingly, a conventional apparatus uses an automatic gain control (abbreviated AGC hereinafter) circuit to gain-control the levels of respective signals reproduced at both the inner and outer tracks. In addition, a so-called write-once optical disk storage uses a gain switching circuit which switches a gain every recording/reproducing to prevent circuitry saturation and maintain constant signal level.
On the other hand, when a 3.5 in optical disk was not conventionally standardized, each company individually developed an optical disk made of a distinctive material and a corresponding optical disk storage. However, now that optical disks are standardized by the ISO standard and ANSI standard, an optical disk storage compatible with optical disks, even if made by other companies however conformable to one of the above standard, is requested.
However, since optical disks made by other companies have various reproduced levels because of the different materials and thus some of levels deviates from an operatable gain range for the AGC circuit in the conventional optical disk storage, the conventional optical disk storage cannot reproduce such an optical disk at its optimum level.